Antenna Replacement Experiment
 

"Richard Clark" wrote in message
...
On Thu, 29 Jan 2009 06:41:17 GMT, "Spin"
wrote:

Is it feasable to remove the ferrite antenna from an am radio & replace
it
with an external multi-turn box loop with the same primary/secondary
inductance?

Those with more than one coil (almost all) are not primary to
secondary relationships. One coil is the RF/Mixer stage, and the
other is the Oscillator stage and the ferrite provides the mixing path
as well as the signal pickup path. If you closely examine the
variable capacitor, you should see that it is also two independent
sections on the same frame (or inside the same enclosure). There
should also be a trimmer for each, one for peaking the RF, the other
for tracking the Oscillator. If there is a TRF stage, it will
probably have another coil/cap combo and probably with that coil as a
separate item.

It would help if you identify the "am radio."

73's
Richard Clark, KB7QHC

This is why you would do just as well to add some turns to the ferrite
loopstick for an external antenna and simply shield the radio. That method
of coupling is very efficient.

Antenna Replacement Experiment
 

"JB" wrote in message
...
"Richard Clark" wrote in message

snip

... you would do just as well to add some turns to the ferrite
loopstick for an external antenna and simply shield the radio. That
method
of coupling is very efficient.

In a weak signal area (metal building, basement, etc), any wire that runs
outside can simply be wrapped a few times around the radio and grounded.
The wrapping direction is dictated by the orientation of the internal
loopstick. With a left-to-right loopstick, you wrap over the top and bottom

When I was in the Navy, I liked having a bedside radio, so that was my
method. On one ship, I was near a door to an open deck, so I snaked a wire
outside and strung about 30 feet of it behind a pipe. On another ship, I
connected my wire through a cap to the telephone wire. I got a lot of
click/pop noise on that one but I had a half-dozen AM stations I could hear
OK.

Best reception job was on a carrier. The "weather-guessers" were high up,
on the 07 level and I ran a cable to my office on the 02 level. They had
their own WEFAX whip antenna feeding an antenna filter panel (AN/SRA-12, if
you know what that is.) They didn't use the BCB output of the filter panel
(but I did). It's good to be the Department Leading Chief.

Antenna Replacement Experiment
 

On Thu, 29 Jan 2009 08:31:28 -0800, Richard Clark
wrote:

On Thu, 29 Jan 2009 06:41:17 GMT, "Spin"
wrote:

Is it feasable to remove the ferrite antenna from an am radio & replace it
with an external multi-turn box loop with the same primary/secondary
inductance?

Those with more than one coil (almost all) are not primary to
secondary relationships. One coil is the RF/Mixer stage, and the
other is the Oscillator stage and the ferrite provides the mixing path
as well as the signal pickup path. If you closely examine the
variable capacitor, you should see that it is also two independent
sections on the same frame (or inside the same enclosure). There
should also be a trimmer for each, one for peaking the RF, the other
for tracking the Oscillator. If there is a TRF stage, it will
probably have another coil/cap combo and probably with that coil as a
separate item.

It would help if you identify the "am radio."

73's
Richard Clark, KB7QHC

Sorry no, they are not going to inject the LO via the loopstick. That
would lead to illegal and unacceptable emissions.

Antenna Replacement Experiment
 

"JosephKK" wrote in message
...
On Thu, 29 Jan 2009 08:31:28 -0800, Richard Clark
wrote:

On Thu, 29 Jan 2009 06:41:17 GMT, "Spin"
wrote:

Is it feasable to remove the ferrite antenna from an am radio & replace
it
with an external multi-turn box loop with the same primary/secondary
inductance?

Those with more than one coil (almost all) are not primary to
secondary relationships. One coil is the RF/Mixer stage, and the
other is the Oscillator stage and the ferrite provides the mixing path
as well as the signal pickup path. If you closely examine the
variable capacitor, you should see that it is also two independent
sections on the same frame (or inside the same enclosure). There
should also be a trimmer for each, one for peaking the RF, the other
for tracking the Oscillator. If there is a TRF stage, it will
probably have another coil/cap combo and probably with that coil as a
separate item.

It would help if you identify the "am radio."

73's
Richard Clark, KB7QHC

Sorry no, they are not going to inject the LO via the loopstick. That
would lead to illegal and unacceptable emissions.


I thought this sounded wrong, and I've certainly never encountered a
domestic receiver designed to radiate its LO! Such a design could wreak
havoc in the medium wave band (where a low-side LO would be in-band for part
of its range).

Chris

Antenna Replacement Experiment
 

On Sun, 01 Feb 2009 10:46:26 -0800, JosephKK
wrote:

Sorry no, they are not going to inject the LO via the loopstick. That
would lead to illegal and unacceptable emissions.

Maybe so.

73's
Richard Clark, KB7QHC